From: Andreas Gruenbacher agruenba@redhat.com
[ Upstream commit 52f3f033a5dbd023307520af1ff551cadfd7f037 ]
During lockless buffered reads, filemap_read() holds page cache page references while trying to copy data to the user-space buffer. The calling process isn't holding the inode glock, but the page references it holds prevent those pages from being removed from the page cache, and that prevents the underlying inode glock from being moved to another node. Thus, we can end up in the same kinds of distributed deadlock situations as with normal (non-lockless) buffered reads.
Fix that by disabling page faults during lockless reads as well.
Signed-off-by: Andreas Gruenbacher agruenba@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/gfs2/file.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c index fa071d738c78..c781c19303db 100644 --- a/fs/gfs2/file.c +++ b/fs/gfs2/file.c @@ -956,14 +956,16 @@ static ssize_t gfs2_file_read_iter(struct kiocb *iocb, struct iov_iter *to) return ret; iocb->ki_flags &= ~IOCB_DIRECT; } + pagefault_disable(); iocb->ki_flags |= IOCB_NOIO; ret = generic_file_read_iter(iocb, to); iocb->ki_flags &= ~IOCB_NOIO; + pagefault_enable(); if (ret >= 0) { if (!iov_iter_count(to)) return ret; written = ret; - } else { + } else if (ret != -EFAULT) { if (ret != -EAGAIN) return ret; if (iocb->ki_flags & IOCB_NOWAIT)